Method of operating a liquefracture handpiece

ABSTRACT

A surgical handpiece having two coaxial tubes or channels mounted within a body. The first tube is used for aspiration and is smaller in diameter than the second tube so as to great an annular passage between the first and second tube. The annular passage communicates with a pumping chamber formed between two electrodes. The pumping chamber works by boiling a small volume of the surgical fluid. As the fluid boils, it expands rapidly, thereby propelling the liquid downstream of the pumping chamber out of the annular passage. The electrodes are insulated from each other.

This application is a divisional application of U.S. patent applicationSer. No. 09/428,744, filed Oct. 28, 1999, now U.S. Pat. No. 6,206,848,which is a continuation of U.S. patent application Ser. No. 09/090,433,filed Jun. 4, 1998 now U.S. Pat. No. 6,080,128.

BACKGROUND OF INVENTION

This invention relates generally to the field of cataract surgery andmore particularly to a handpiece for practicing the liquefracturetechnique of cataract removal.

The human eye in its simplest terms functions to provide vision bytransmitting light through a clear outer portion called the cornea, andfocusing the image by way of the lens onto the retina. The quality ofthe focused image depends on many factors including the size and shapeof the eye, and the transparency of the cornea and lens.

When age or disease causes the lens to become less transparent, visiondeteriorates because of the diminished light which can be transmitted tothe retina. This deficiency in the lens of the eye is medically known asa cataract. An accepted treatment for this condition is surgical removalof the lens and replacement of the lens function by an artificialintraocular lens (IOL).

In the United States, the majority of cataractous lenses are removed bya surgical technique called phacoemulsification. During this procedure,a thin phacoemulsification cutting tip is inserted into the diseasedlens and vibrated ultrasonically. The vibrating cutting tip liquifies oremulsifies the lens so that the lens may be aspirated out of the eye.The diseased lens, once removed, is replaced by an artificial lens.

A typical ultrasonic surgical device suitable for ophthalmic proceduresconsists of an ultrasonically driven handpiece, an attached cutting tip,and irrigating sleeve and an electronic control console. The handpieceassembly is attached to the control console by an electric cable andflexible tubings. Through the electric cable, the console varies thepower level transmitted by the handpiece to the attached cutting tip andthe flexible tubings supply irrigation fluid to and draw aspirationfluid from the eye through the handpiece assembly.

The operative part of the handpiece is a centrally located, hollowresonating bar or horn directly attached to a set of piezoelectriccrystals. The crystals supply the required ultrasonic vibration neededto drive both the horn and the attached cutting tip duringphacoemulsification and are controlled by the console. The crystal/hornassembly is suspended within the hollow body or shell of the handpieceby flexible mountings. The handpiece body terminates in a reduceddiameter portion or nosecone at the body's distal end. The nosecone isexternally threaded to accept the irrigation sleeve. Likewise, the hornbore is internally threaded at its distal end to receive the externalthreads of the cutting tip. The irrigation sleeve also has an internallythreaded bore that is screwed onto the external threads of the nosecone.The cutting tip is adjusted so that the tip projects only apredetermined amount past the open end of the irrigating sleeve.Ultrasonic handpieces and cutting tips are more fully described in U.S.Pat. Nos. 3,589,363; 4,223,676; 4,246,902; 4,493,694; 4,515,583;4,589,415; 4,609,368; 4,869,715; 4,922,902; 4,989,583; 5,154,694 and5,359,996, the entire contents of which are incorporated herein byreference.

In use, the ends of the cutting tip and irrigating sleeve are insertedinto a small incision of predetermined width in the cornea, sclera, orother location. The cutting tip is ultrasonically vibrated along itslongitudinal axis within the irrigating sleeve by the crystal-drivenultrasonic horn, thereby emulsifying the selected tissue in situ. Thehollow bore of the cutting tip communicates with the bore in the hornthat in turn communicates with the aspiration line from the handpiece tothe console. A reduced pressure or vacuum source in the console draws oraspirates the emulsified tissue from the eye through the open end of thecutting tip, the cutting tip and horn bores and the aspiration line andinto a collection device. The aspiration of emulsified tissue is aidedby a saline flushing solution or irrigant that is injected into thesurgical site through the small annular gap between the inside surfaceof the irrigating sleeve and the cutting tip.

Recently, a new cataract removal technique has been developed thatinvolves the injection of hot (approximately 45° C. to 105° C.) water orsaline to liquefy or gellate the hard lens nucleus, thereby making itpossible to aspirate the liquefied lens from the eye. Aspiration isconducted concurrently with the injection of the heated solution and theinjection of a relatively cool solution, thereby quickly cooling andremoving the heated solution. This technique is more fully described inU.S. Pat. No. 5,616,120 (Andrew, et al.), the entire content of which isincorporated herein by reference. The apparatus disclosed in thepublication, however, heats the solution separately from the surgicalhandpiece. Temperature control of the heated solution can be difficultbecause the fluid tubings feeding the handpiece typically are up to twometers long, and the heated solution can cool considerably as it travelsdown the length of the tubing.

U.S. Pat. No. 5,885,243 (Capetan, et al.) discloses a handpiece having aseparate pumping mechanism and resistive heating element. Such astructure adds unnecessary complexity to the handpiece.

Therefore, a need continues to exist for a simple surgical handpiecethat can heat internally the solution used to perform the liquefracturetechnique.

BRIEF SUMMARY OF THE INVENTION

The present invention improves upon the prior art by providing asurgical handpiece having two coaxially mounted tubes or channelsmounted to a body. The first tube is used for aspiration and is smallerin diameter than the second tube so as to create an annular passagebetween the first and second tube. The annular gap communicates with apumping chamber formed between two electrodes. The pumping chamber worksby boiling a small volume of the surgical fluid. As the fluid boils, itexpands rapidly, thereby propelling the liquid downstream of the pumpingchamber out of the annular gap. The electrodes are insulated from eachother.

Accordingly, one objective of the present invention is to provide asurgical handpiece having at least two coaxial tubes.

Another objective of the present invention is to provide a handpiecehaving a pumping chamber.

Another objective of the present invention is to provide a surgicalhandpiece having a device for delivering the surgical fluid through thehandpiece in pulses.

Still another objective of the present invention is to provide ahandpiece having a pumping chamber formed by two electrodes.

Yet another objective of the present invention is to provide a handpiecehaving two electrodes wherein the electrodes are insulated.

These and other advantages and objectives of the present invention willbecome apparent from the detailed description and claims that follow.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a front, upper left perspective view of a first embodiment ofthe handpiece of the present invention.

FIG. 2 is a rear, upper right perspective view of a first embodiment ofthe handpiece of the present invention.

FIG. 3 is a cross-sectional view of a first embodiment of the handpieceof the present invention taken along a plane passing through theirrigation channel.

FIG. 4 is a cross-sectional view of a first embodiment of the handpieceof the present invention taken along a plane passing through theaspiration channel.

FIG. 5 is an enlarged partial cross-sectional view of a first embodimentof the handpiece of the present invention taken at circle 5 in FIG. 4.

FIG. 6 is an enlarged partial cross-sectional view of a first embodimentof the handpiece of the present invention taken at circle 6 in FIG. 3.

FIG. 7 is an enlarged cross-sectional view of a first embodiment of thehandpiece of the present invention taken at circle 7 in FIGS. 3 and 4.

FIG. 8 is a partial cross-sectional view of a second embodiment of thehandpiece of the present invention.

FIG. 9 is an enlarged partial cross-sectional view of the secondembodiment of the handpiece of the present invention taken at circle 9in FIG. 8.

FIG. 10 is an enlarged partial cross-sectional view of the pumpingchamber used in the second embodiment of the handpiece of the presentinvention taken at circle 10 in FIG. 9.

FIG. 11 is a partial cross-sectional view of a third embodiment of thehandpiece of the present invention.

FIG. 12 is an enlarged partial cross-sectional view of the distal end ofthe third embodiment of the handpiece of the present invention taken atcircle 12 in FIG. 11.

FIG. 13 is an enlarged partial cross-sectional view of the pumpingchamber used in the third embodiment of the handpiece of the presentinvention shown in FIGS. 11 and 12.

FIG. 14 is a block diagram of a control system that can be used with thehandpiece of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Handpiece 10 of the present invention generally includes handpiece body12 and operative tip 16. Body 12 generally includes external irrigationtube 18 and aspiration fitting 20. Body 12 is similar in construction towell-known in the art phacoemulsification handpieces and may be madefrom plastic, titanium or stainless steel. As best seen in FIG. 6,operative tip 16 includes tip/cap sleeve 26, needle 28 and tube 30.Sleeve 26 may be any suitable commercially available phacoemulsificationtip/cap sleeve or sleeve 26 may be incorporated into other tubes as amulti-lumen tube. Needle 28 may be any commercially available hollowphacoemulsification cutting tip, such as the TURBOSONICS tip availablefrom Alcon Laboratories, Inc., Fort Worth, Tex. Tube 30 may be anysuitably sized tube to fit within needle 28, for example 29 gaugehypodermic needle tubing.

As best seen in FIG. 5, tube 30 is free on the distal end and connectedto pumping chamber 42 on the proximal end. Tube 30 and pumping chamber42 may be sealed fluid tight by any suitable means having a relativelyhigh melting point, such as a silicone gasket, glass frit or silversolder. Fitting 44 holds tube 30 within bore 48 of aspiration horn 46.Bore 48 communicates with fitting 20, which is journaled into horn 46and sealed with O-ring seal 50 to form an aspiration pathway throughhorn 46 and out fitting 20. Horn 46 is held within body 12 by O-ringseal 56 to form irrigation tube 52 which communicates with irrigationtube 18 at port 54.

As best seen in FIG. 7, in a first embodiment of the present invention,pumping chamber 42 contains a relatively large pumping reservoir 43 thatis sealed on both ends by electrodes 45 and 47. Electrical power issupplied to electrodes 45 and 47 by insulated wires, not shown. In use,surgical fluid (e.g. saline irrigating solution) enters reservoir 43 25through port 55, tube 34 and check valve 53, check valves 53 beingwell-known in the art. Electrical current (preferably Radio FrequencyAlternating Current or RFAC) is delivered to and across electrodes 45and 47 because of the conductive nature of the surgical fluid. As thecurrent flows through the surgical fluid, the surgical fluid boils. Asthe surgical fluid boils, it expands rapidly out of pumping chamber 42through port 57 and into tube 30 (check valve 53 prevents the expandingfluid from entering tube 34). The expanding gas bubble pushes thesurgical fluid in tube 30 downstream of pumping chamber 42 forward.Subsequent pulses of electrical current form sequential gas bubbles thatmove surgical fluid down tube 30. The size and pressure of the fluidpulse obtained by pumping chamber 42 can be varied by varying thelength, timing and/or power of the electrical pulse sent to electrodes45 and 47 and by varying the dimensions of reservoir 43. In addition,the surgical fluid may be preheated prior to entering pumping chamber42. Preheating the surgical fluid will decrease the power required bypumping chamber 42 and/or increase the speed at which pressure pulsescan be generated.

As best seen in FIGS. 8-10, in a second embodiment of the presentinvention, handpiece 110 generally includes body 112, having powersupply cable 113, irrigation/aspiration lines 115, pumping chambersupply line 117. Distal end 111 of handpiece 110 contains pumpingchamber 142 having a reservoir 143 formed between electrodes 145 and147. Electrodes 145 and 147 are preferably made from aluminum, titanium,carbon or other similarly conductive materials and are electricallyinsulated from each other and body 112 by anodized layer 159 formed onelectrodes 145 and 147. Anodized layer 159 is less conductive thanuntreated aluminum and thus, acts as an electrical insulator. Electrodes145 and 147 and electrical terminals 161 and 163 are not anodized andthus, are electrically conductive. Layer 159 may be formed by anysuitable anodization technique, well-known in the art, and electrodes145 and 147 and electrical terminals 161 and 163 may be masked duringanodization or machined after anodization to expose bare aluminum.Electrical power is supplied to electrodes 145 and 147 through terminals161 and 163 and wires 149 and 151, respectively. Fluid is supplied toreservoir 143 though supply line 117 and check valve 153. Extendingdistally from pumping chamber 142 is outer tube 165 that coaxiallysurrounds aspiration tube 167. Tubes 165 and 167 may be of similarconstruction as tube 30. Tube 167 is of slightly smaller diameter thantube 165, thereby forming an annular passage or gap 169 between tube 165and tube 167. Annular gap 169 fluidly communicates with reservoir 143.

In use, surgical fluid enters reservoir 143 through supply line 117 andcheck valve 153. Electrical current is delivered to and acrosselectrodes 145 and 147 because of the conductive nature of the surgicalfluid. As the current flows through the surgical fluid, the surgicalfluid boils. As the surgical fluid boils, it expands rapidly out ofpumping chamber 142 through annular gap 169. The expanding gas bubblepushes forward the surgical fluid in annular gap 169 downstream ofpumping chamber 142. Subsequent pulses of electrical current formsequential gas bubbles that move or propel the surgical fluid downannular gap 169.

One skilled in the art will recognize that the numbering in FIGS. 8-10is identical to the numbering in FIGS. 1-7 except for the addition of“100” in FIGS. 8-10. As best seen in FIGS. 11-13, in a third embodimentof the present invention, handpiece 210 generally includes body 212,having power supply cable 213, irrigation/aspiration lines 215, pumpingchamber supply line 217. Distal end 211 of handpiece 210 containspumping chamber 242 having a reservoir 243 formed between electrodes 245and 247. Electrodes 245 and 247 are preferably made from aluminum andelectrically insulated from each other and body 212 by anodized layer259 formed on electrodes 245 and 247. Anodized layer 259 is lessconductive than untreated aluminum and thus, acts as an electricalinsulator. Electrodes 245 and 247 and electrical terminals 261 and 263are not anodized and thus, are electrically conductive. Layer 259 may beformed by any suitable anodization technique, well-known in the art, andelectrodes 245 and 247 and electrical terminals 261 and 263 may bemasked during anodization or machined after anodization to expose barealuminum. Electrical power is supplied to electrodes 245 and 247 throughterminals 261 and 263 and wires 249 and 251, respectively. Fluid issupplied to reservoir 243 though supply line 217 and check valve 253.Extending distally from pumping chamber 242 is outer tube 265 thatcoaxially surrounds aspiration tube 267. Tubes 265 and 267 may be ofsimilar construction as tube 30. Tube 267 is of slightly smallerdiameter than tube 265, thereby forming an annular passage or gap 269between tube 265 and tube 267. Annular gap 269 fluidly communicates withreservoir 243.

In use, surgical fluid enters reservoir 243 through supply line 217 andcheck valve 253. Electrical current is delivered to and acrosselectrodes 245 and 247 because of the conductive nature of the surgicalfluid. As the current flows through the surgical fluid, the surgicalfluid boils. The current flow progresses from the smaller electrode gapsection to the larger electrode gap section, i.e., from the region oflowest electrical resistance to the region of higher electricalresistance. The boiling wavefront also progresses from the out ofpumping chamber 242 through annular gap 269. The expanding gas bubblepushes forward the surgical fluid in annular gap 269 downstream ofpumping chamber 242. Subsequent pulses of electrical current formsequential gas bubbles that move or propel the surgical fluid downannular gap 269.

One skilled in the art will recognize that the numbering in FIGS. 11-13is identical to the numbering in FIGS. 1-7 except for the addition of“200” in FIGS. 11-13.

While several embodiments of the handpiece of the present invention aredisclosed, any handpiece producing adequate pressure pulse force,temperature, rise time and frequency may also be used. For example, anyhandpiece producing a pressure pulse force of between 0.02 grams and20.0 grams, with a pressure pulse force rise time of between 1 gram/sec.and 20,000 grams/sec and a frequency of between 1 Hz and 200 Hz may beused, with between 10 Hz and 100 Hz being most preferred. The pressurepulse force and frequency will vary with the hardness of the materialbeing removed. For example, the inventors have found that a lowerfrequency with a higher pulse force is most efficient at debulking andremoving the relatively hard nuclear material, with a higher frequencyand lower pulse force being useful in removing softer epinuclear andcortical material. Infusion pressure, aspiration flow rate and vacuumlimit are similar to current phacoemulsification techniques.

As seen in FIG. 10, one embodiment of control system 300 for use inoperating handpiece 310 includes control module 347, power gain RFamplifier 312 and function generator 314. Power is supplied to RFamplifier 312 by DC power supply 316, which preferably is an isolated DCpower supply operating at several hundred volts, but typically ±200volts. Control module 347 may be any suitable microprocessor, microcontroller, computer or digital logic controller and may receive inputfrom operator input device 318. Function generator 314 provides theelectric wave form in kilohertz to amplifier 312 and typically operatesat around 450 KHz or above to help minimize corrosion.

In use, control module 347 receives input from surgical console 320.Console 320 may be any commercially available surgical control consolesuch as the LEGACY® SERIES TWENTY THOUSANDS® surgical system availablefrom Alcon Laboratories, Inc., Fort Worth, Tex. Console 320 is connectedto handpiece 310 through irrigation line 322 and aspiration line 324,and the flow through lines 322 and 324 is controlled by the user viafootswitch 326. Irrigation and aspiration flow rate information inhandpiece 310 is provided to control module 347 by console 320 viainterface 328, which may be connected to the ultrasound handpiececontrol port on console 320 or to any other output port. Control module347 uses footswitch 326 information provided by console 320 and operatorinput from input device 318 to generate two control signals 330 and 332.Signal 332 is used to operate pinch valve 334, which controls thesurgical fluid flowing from fluid source 336 to handpiece 310. Fluidfrom fluid source 336 is heated in the manner described herein. Signal330 is used to control function generator 314. Based on signal 330,function generator 314 provides a wave form at the operator selectedfrequency and amplitude determined by the position of footswitch 326 toRF amplifier 312 which is amplified to advance the powered wave formoutput to handpiece 310 to create heated, pressurized pulses of surgicalfluid.

Any of a number of methods can be employed to limit the amount of heatintroduced into the eye. For example, the pulse train duty cycle of theheated solution can be varied as a function of the pulse frequency sothat the total amount of heated solution introduced into the eye doesnot vary with the pulse frequency. Alternatively, the aspiration flowrate can be varied as a function of pulse frequency so that as pulsefrequency increases aspiration flow rate increases proportionally.

This description is given for purposes of illustration and explanation.It will be apparent to those skilled in the relevant art that changesand modifications may be made to the invention described above withoutdeparting from its scope or spirit. For example, it will be recognizedby those skilled in the art that the present invention may be combinedwith ultrasonic and/or rotating cutting tips to enhance performance.

We claim:
 1. A method of operating a liquefracture handpiece, thehandpiece having a body and a pumping chamber contained within the body,the method comprising the steps of: a) operating the pumping chamber ata pulse frequency to produce pressure pulses having a pressure pulseforce of between 0.02 grams and 20.0 grams; b) varying the pulsefrequency; and c) varying an aspiration flow rate as a function of thepulse frequency.
 2. The method of claim 1 wherein the pressure pulseshave a rise time of between 1 gram/second and 20,000 grams/second.
 3. Amethod of operating a liquefracture handpiece, the handpiece having abody and a pumping chamber contained within the body, the methodcomprising the steps of: a) operating the pumping chamber at a pulsefrequency and with a pulse train duty cycle to produce pressure pulseshaving a pressure pulse force of between 0.02 grams and 20.0 grams; b)varying the pulse frequency; and c) varying the pulse train duty cycleas function of the pulse frequency.
 4. The handpiece of claim 3 whereinthe pressure pulses have a rise time of between 1 gram/second and 20,000grams/second.
 5. A method of operating a liquefracture handpiece, thehandpiece having a body and a pumping chamber contained within the body,the method comprising the steps of: a) operating the pumping chamber ata predetermined operating parameter so as to produce a pulse streamhaving a plurality of pressure pulses, the pressure pulses having apressure pulse force of between 0.02 grams and 20.0 grams; and b)varying the operating parameter so as to vary the coherence length ofthe pulse stream.
 6. The method of claim 5 wherein the pressure pulseshave a rise time of between 1 gram/second and 20,000 grams/second. 7.The method of claim 5 wherein the parameter is flow development.
 8. Themethod of claim 5 wherein the parameter is pressure.
 9. The method ofclaim 5 wherein the parameter is temperature.